KINETICS OF REDUCTION OF MNO IN POWDER MIXTURES WITH CARBON

Experimental data on the kinetics of the reaction between MnO and grap hite in a mixture of fine powders, obtained earlier by one of the auth ors, were reassessed. The principal motive was to test on this system a new kinetic model, the ''intrinsic transport'' model, published prev iously by the present authors. In this model, the reaction-rate-limiti ng step is assumed to be transport of a gaseous intermediate by pore d iffusion between reaction sites on the surfaces of the reactant partic les. Various other model formalisms potentially applicable to this rea ction also were tested. It is shown that the intrinsic transport of CO 2 gave good to excellent fits to the experimental data over a wide ran ge of reaction conditions. Other models gave poor agreement. It is sho wn, furthermore, that for the case where the CO2 pore-diffusion path l engths were made small (fine MnO and coarse graphite particle size), t hus speeding up rapid intrinsic transport, the graphite-surface reacti on became rate controlling.